Electric switches



April 5, 1960 Y WILSON 2,931,875

ELECTRIC SWITCHES Filed Nov. 5, 1958 2 Sheets-Sheet 1 lo M l6 l2 22 -5 I3 Fig.|.

WITNESSES INVENTOR 5 John Wilson 6 AT T'o R N E Y I April 5, .1960 .WILSQN 2,931,875

ELECTRIC SWITCHES Filed Nov. 3, 1958 2 Sheets-Sheet 2 Fig.3.

United States Patent ELECTRIC swrrcnas John Wilson, Hamilton, Ontario, Canada, assignor to Canadian Westinghouse Company, Limited, Hamilton, Ontario, Canada Application November 3, 1958, Serial No. 771,552 Claims priority, application Canada May 17, 1958 Claims. (Cl. 200-153) The present invention is concerned with improvements in and relating to electric switches, and especially to such switches intended for use as circuit breakers in high power electric installations.

Electric switches intended for operation as circuit breakers in high power electric installations are of mas sive construction owing to the very high currents involved, e.g., of the order of several hundred amperes, and consequently their moving parts have high inertias. In order to avoid the formation of arcs upon opening and ciosing the switches, it is usual to move the switch contacts relative to one another at comparatively high velocity. A special difiiculty is experienced when closing such switches in that, although the contacts are required to move together at high velocity, at least during the initial part of their movement, their relative velocity when they meet should be as low as is permissible for safe operation, in order to avoid physical damage on impact.

it is also a requirement of such switches that the mechanism employed for moving the contacts should be as small and as compact as possible in order to keep the dimensions of the whole apparatus small, especially the height of the apparatus.

Accordingly, it is an object of the present invention to provide an electric switch, especially an electric switch adapted for use as a circuit breaker in high power electric installations, with which positive and accurate control of the velocity of, the moving contacts can be achieved.

It is also an object of the invention to provide a switch as specified immediately above in which the control ap paratus for moving the movable contacts is of relatively compact form.

According to the present invention, there is provided an electric switch comprising relatively movable contact members and means for moving said contact members to close the switch at a high initial velocity and at a lower velocity on operative contact of the members, said means comprising a thrust transmitting lever operatively connected to one contact member and pivoted to a stationary partof the switch, a rotatable driving member which is rotated to open and close the switch, an articulated linkage including a cam follower and connected between the saidlever and driving member, and a cam mounted on a stationary part of the switch, engaged by the said cam follower and determining the velocity of movement of the said one contact member upon rotation of the driving member to open and close the switch.

A specific embodiment of my invention will now be described, by way of example, with reference to the accompanying drawings wherein:

Figure 1 is a section through part of a three-phase circuit breaker switch to show mainly the control mechanism for moving the moving contacts, the switch mechanism being shown with the said contacts in the closed position thereof; g

' Fig. 2 is a plan view of the mechanism shown in Fig. 1; and

Fig. 3 is a section similar to Fig. 1, but showing the switch mechanism set so that the moving contacts are in the open position thereof.

Referring now to the drawings, the switch comprises a heavy metal casing 1 enclosing all the moving parts thereof, and provided to one side with an extension 2 to accommodate the control mechanism. The switch proper comprises three rods 3 (one for each phase) mounted for vertical sliding movement Within the casing by means which are not shown, the lower end of each rod (i.e., when the switch is in position for operation) carrying a moving bridge contact 4, which connects together two stationary contacts, represented in Fig. 1 only by 5 and 6, in order to close the switch. A yoke frame '7 having a pair of yokes 8 pivoted thereto on pins such as 9, is clamped to the upper ends of the rods 3. A two-armed thrust transmitting lever 10 has the ends of its arms pivoted to the respective yokes 8 on pins 11, and its other end is pivoted tothe casing extension 2 on an axle 12. Movement of the lever 10 about the axle i2 and the resultant vertical sliding movement of the rods 3 are produced by an articulated linkage comprising a short arm 13, a pair of parallel short arms 14 and a. pair of connecting long arms 15. The short arm 13 is pivotally mounted in the casing extension 2 by a hexagonal section shaft 15 passing through one end of the arm, the shaft 16 being rotatable by means of a tool or a motor applied to an end 16A (Fig. 2) of the shaft which projects outside the casing. The other end of the short arm 13 is pivoted by a pin 17 to the adjacent ends of the pair of connecting arms 15, the other ends of the latter being in turn pivotally connected by a pin 18 to the adjacent ends of the pair of short arms 14. The other ends of the short arms 14 are pivoted by a pin 19 to the lever 10 at a point intermediate the ends of that lever. The pin 18 carries a cam roller 20 which is freely rotatable thereon and is engageable with a first fixed cam 21 mounted rigidly on the casing extension 2. A second movable cam 22 is fixed rigidly to one of the arms 15 and is engageable with the axle 12.

To open the switch, the shaft 16 is rotated by a tool or a motor as described above and in a clockwise direction (as seen in Fig. 1 of the drawings), the arms 13 and 14 also moving clockwise and the arm 15 moving to the left.

Immediately upon the said movement of the connection arm 15, the movable cam 22 engages the fixed axle 12 and biases the arm 15 for downward movement thus ensuring that the cam roller 20 on the pin 18 remains in engagement with the fixed cam 21 and also that the lever 10, the rods 3 and the respective bridge contacts 4, are moved positively downwards.

To close the switch, the shaft 16 is rotated anti-clock fixed cam 21. The part of the cam profile which is engaged by the cam roller 20 during the initial stages of closing (i.e., the left-hand part as seen in the drawings) is of relatively steep slope, so that initially the contacts 4 move at relatively high velocity toward the respective contacts 5 and 6. As the cam roller proceeds along the cam, the slope of the profile of the cam decreases until, at the part thereof corresponding to the point of closure of the switch contacts, the slope is at a minimum and the closure takes place at relatively low velocity.

The movable cam 22 serves as an interlock if the switch contacts become welded in the closed position, since it prevents movement of the mechanism to the open position without a corresponding opening movement of the contacts. Moreover, it ensures that inertial effects do not permit the lever and the rods 3, etc. to overshoot the control provided by the fixed cam 21 and its cooperating cam roller 2%), and also that there is no possibility of the contacts bouncing as they close. The profiles of the two cams 21 and 22 are thus such as to ensure positive control of the movement of the lever 16, and rods 3 and their contacts 4 throughout their range of movement. Having described the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made in the structural details and the combination of elements disclosed without departing from the spirit of the invention.

I claim as my invention:

1. An electric switch comprising relatively movable contact members andmeans for moving said contact members to close the switch at a high initial velocity and at a lower velocity on operative contact of the members, said means comprising a thrust transmitting lever operatively connected to one contact member and pivoted to a stationary part of the switch, a rotatable driving memher which is rotated to open and close the switch, an articulated linkage including a cam follower and connected between the said lever and driving member, and a cam mounted on a stationary part of the switch, said cam being engaged by said cam follower to determine the velocity of movement of the said one contact member upon rotation of the driving member to open and close the switch.

2. An electric switch comprising relatively movable contact members and means for moving said contact members to close the switch at a high initial velocity and at a lower velocity on operative contact of the members, said means comprising a thrust transmitting lever operatively connected to one contact member and pivoted to a stationary part of the switch, a rotatable driving member which is rotated to open and close the switch, an articulated linkage including a cam follower and connected between the said lever and driving member, a cam mounted on a stationary part of the switch and engaged by the said cam follower to determine the velocity of movement of the said one contact member upon rotation of the driving member to open and close the switch, and said articulated linkage including a second cam operative upon movement of said articulated linkage to maintain said cam follower in engagement with said first-mentioned cam.

3. An electric switch comprising relatively movable contact members and means for moving said contact members to close the switch at a high initial velocity and at a lower velocity on operative contact of the members, said means comprising a thrust transmitting lever operatively connected at one end to one contact member and pivoted at the other end to a stationary part of the switch, a rotatable driving member which is rotated to open and close the switch, an articulated linkage including a first arm rotatable with the driving member, a second arm pivoted to the thrust transmitting lever intermediate the ends of the lever, and a third arm connecting together the first and second arms, a cam follower at the junction of the said first and third arms, a cam mounted on a stationary part of the switch, and said cam being engaged by said cam follower for determining the velocity of movement of the said one contact member upon rotation of the driving member to open and close the switch.

4. An electric switch comprising relatively movable contact members and means for moving said contact members to close the switch at a high initial velocity and at a lower velocity on operative contact of the members, said means comprising a thrust transmitting lever operatively connected at one end to one contact member and pivoted at the other end to a stationary part of the switch, a rotatable driving member which is rotated to open and close the switch, an articulated linkage ineluding a first arm rotatable with the driving member, a second arm pivoted to the thrust transmitting lever intermediate the ends of the lever, and a third arm connecting together the first and second arms, a cam follower at the junction of the said first and third arms, a cam mounted on a stationary part of the switch, said cam being engaged by the said cam follower to determine the velocity of movement of the said one contact member upon rotation of the driving member to open and close the switch, and a second cam mounted on said third arm operative upon movement of said articulated linkage to maintain said cam follower in engagement with said first-mentioned cam.

5. An electric switch comprising relatively movable contact members and means for moving said contact members to close the switch at a high initial velocity and at a lower velocity on operative contact of the members, said means comprising a thrust transmitting lever operatively connected at one end to one contact member and pivoted at the other end to a stationary part of the switch, a rotatable driving member which is rotated to open and close the switch, an articulated linkage including a first arm rotatable with the driving member, a second arm pivoted to the thrust transmitting lever intermediate the ends of the lever, and a third arm connecting together the first and second arms, a cam follower at the junction of the said first and third arms, a cam mounted on a stationary part of the switch, said cam being engaged by the said cam follower to determine the velocity of movement of the said one contact member upon rotation of the driving member to open and close the switch, and a second cam mounted on said third arm engaging the pivot of said thrust transmitting lever upon movement of said articulated linkage to maintain said cam follower in engagement with said first-mentioned cam.

6. An electric switch comprising a switch casing, relatively movable contact members mounted within the easing and means for moving said contact members to close the switch at a high initial velocity and at a lower velocity on operative contact of the members, said means comprising a thrust transmitting lever operatively connected to one contact member and pivoted to the switch casing within a casing extension to one side of the casing, a rotatable driving member which is mounted within the said casing extension and is rotated to open and close the switch, an articulated linkage accommodated within the casing extension, the articulated linkage including a cam follower and being connected between the said lever and driving member, and a cam mounted on a stationary part of the switch and being engaged by the said cam follower to determine the velocity of movement of the said one contact member upon rotation of the driving member to open and close the switch.

7. An electric switch comprising a switch casing, stationary and movable contact means mounted within the casing and means for moving said movable contact means to close said switch at high initial velocity and at a lower velocity upon engagement of said contact means, said means comprising a thrust transmitting lever operatively connected to said movable contact means and pivotally supported on said switch casing within a casing extension at one side of said casing, a rotatable drive member mounted within said casing extension and rotatable to open and close said switch, an articulated linkage disposed in said casing extension and including a first arm rotatable with said drive member, a second arm pivoted to said thrust transmitting lever intermediate the ends of said lever, a third arm connecting said first and second arms, a cam mounted on a stationary part of said switch, a cam follower connected between said thrust transmitting lever and said driving member at the junction of said second and third arms and engaging said cam to determine the velocity of movement of said movable contact means upon rotation of said driving member to open and close said switch,

at one side of said casing, a rotatable drive member mounted within said casing extension and rotatable to open and close said switch, an articulated linkage disposed in said casing extension and including a first arm rotatable with said drive member, a second arm pivoted to said thrust transmitting lever intermediate the ends of said lever, a third arm connecting said first and second arms, a cam mounted on a stationary part of said switch, a cam follower connected between said thrust transmitting lever and said driving member at the junction of said second and third arms and engaging said cam to determine the velocity of movement of said movable contact means upon rotation of said driving member to open and close said switch, and a second cam mounted on said third arm operable upon movement of said articulated linkage to maintain said cam follower in engagement with said first-mentioned cam.

9. An electrical switch comprising stationary and movable contact members, means including an operating rod connected to said movable contact member for moving said movable contact member to close said contacts with a high initial velocity and at a lower velocity upon engagement of said contact members, a thrust transmitting lever having one end connected to said operating rod and the I} t; other end pivotally supported on a fixed part of said switch, a rotatable driving member operable to open and close said contact members, an articulated linkage including a cam follower and connected between said lever and said driving member, and a stationary cam disposed to be engaged by said cam follower to determine the velocity of movement of said movable contact member upon rotation of said driving member to open and close said switch.

10. An electrical switch comprising stationary and movable contact members, means including an operating rod connected to said movable contact members for moving said movable contact members to close said contacts with a high initial velocity and at a lower velocity upon engagement of said contact members, a thrust transmitting lever having one end connected to said operating rod and the other end pivotally supported on a fixed part of said switch, a rotatable driving member operable to open and close said contact members, an articulated linkage including a cam follower and connected between said lever and said driving member, a stationary cam disposed to be engaged by said cam follower to determine the velocity of movement of said movable contact member upon rotation of said driving member to open and close said switch, and a second cam operable on movement of said articulated linkage to maintain said cam follower in engagement with said first-mentioned cam.

References Cited in the file of this patent UNITED STATES PATENTS 2,137,000 Deans Nov. 15, 1938 

